The present invention relates to a means of controlling reradiation, or reflection, from electrically conducting structures, such as linear conductors in the form of cable guy wires, by controlling the current distribution on the conductors by means of inductive effects resulting from the use of high magnetic permeability sleeve-like materials.
The present invention further provides a means of controlling the amplitude and phase distribution of an electromagnetic current on certain conductors by the appropriate location of suitably-sized high magnetic permeability cylindrical sleeves surrounding the conductor.
When electromagnetic radiation, such as from AM radio antennae, or directional antennae, occurs, the electromagnetic radiation emitted by the antennae may be adversely affected by tall towers, such as television towers, that are positioned nearby. For example, cable guy wires are used to support such tall towers. The electromagnetic radiation incident upon the tower will generate currents that flow within such cable guy wires. Undesirable currents can flow not only in the cable guy wires that support the tall towers, but in the tall tower structure itself. These currents result in reradiation or reflection of the incident electromagnetic radiation.
It is known in the art to eliminate the undesirable reradiation caused by the guy wires, or other conducting cables, by dividing the cable into shorter segments by means of insulators that separate the cable segments to reduce the current flow in each section. The effect of the insulators, however, is to provide a capacitance between the various cable segments, and thus the current is not completely open circuited through the conductor.
In order to further reduce the current distribution along a cable that is electrically conductive, it is known to provide an inductance in parallel with the capacitance caused by the insulators so that the net impedance between adjacent cable segments will be very large. The concept of dividing a support cable into a plurality of cable segments separated by insulators and, by providing inductors in parallel with the insulators, has been suggested by Dr. Andrew Alford and is disclosed in application Ser. Nos. 808,290, filed on June 20, 1977, now abandoned and 813,763 filed on July 7, 1977. Dr. Alford has suggested that for specific lengths of cable segments, a current distribution can be achieved which will result in very small, nearly zero, reradiation in the equatorial plane back toward the original electromagnetic source.
The present invention comprises an improvement over the prior art methods of dividing a cable support element, such as a guy wire for tall towers, into segments, with insulators interconnecting the segments and with inductive elements connected in parallel across the insulators. In particular, it is an object of the present invention to provide a means for minimizing reradiation, or reflection, in electrical conductors, such as guy wires or the like, without dividing the guy wires into separate discrete cable segments.
It is further an object of this invention to provide for a new and unique method and apparatus for eliminating reflection, or reradiation, caused by electrically conducting structures, such as cable guy wires, by providing sleeve-like high permeability materials spaced at predetermined distances along the cable guy wire without interrupting the cable guy wire.
It is a further object of the present invention to provide a method and apparatus comprising a sleeve of high magnetic permeability material having an annular cylindrical shape and a specific predetermined length, such that by proper positioning of the sleeve around the cable guy wires, reradiation, or reflection, at a particular electromagnetic radiation frequency can be optimally reduced. In particular, it is an object of the present invention to position the sleeves at particular spaced-apart distances along the guy wire, or other electrical conducting structure, such that the structure approximates, in terms of its electrical characteristic, a structure having a plurality of cable segments interconnected by insulators with inductors connected in parallel across the insulators. The present invention, however, does not require that the cable guy wire be physically separated into shorter cable segments with insulators interconnected therebetween. Thus, the present invention provides for an inexpensive and relatively simple method of retrofitting existing cable guy wire support structures.
These and other objects of the invention will be apparent to one of ordinary skill in the art from reading the following disclosure.